BACTOX, a rapid bioassay that uses protozoa to assess the toxicity of bacteria.

A new type of toxicity test based on the protozoan Tetrahymena pyriformis has been developed to assess the overall toxicity of bacterial strains given as prey. This simple and rapid test is able to detect toxicant-producing bacteria, which may present a biohazard. It can also be used for the risk assessment of microbes designed for deliberate release.

Isolation of Thermus strains from hot composts (60 to 80 degrees C).

High numbers (10(7) to 10(10) cells per g [dry weight]) of heterotrophic, gram-negative, rod-shaped, non-sporeforming, aerobic, thermophilic bacteria related to the genus Thermus were isolated from thermogenic composts at temperatures between 65 and 82 degrees C. These bacteria were present in different types of wastes (garden and kitchen wastes and sewage sludge) and in all the industrial composting systems studied (open-air windows, boxes with automated turning and aeration, and closed bioreactors with aeration). Isolates grew fast on a rich complex medium at temperatures between 40 and 80 degrees C, with optimum growth between 65 and 75 degrees C. Nutritional characteristics, total protein profiles, DNA-DNA hybridization (except strain JT4), and restriction fragment length polymorphism profiles of the DNAs coding for the 16S rRNAs (16S rDNAs) showed that Thermus strains isolated from hot composts were closely related to Thermus thermophilus HB8. These newly isolated T. thermophilus strains have probably adapted to the conditions in the hot-compost ecosystem. Heterotrophic, ovalspore-forming, thermophilic bacilli were also isolated from hot composts, but none of the isolates was able to grow at temperatures above 70 degrees C. This is the first report of hot composts as habitats for a high number of thermophilic bacteria related to the genus Thermus. Our study suggests that Thermus strains play an important role in organic-matter degradation during the thermogenic phase (65 to 80 degrees C) of the composting process.

Phylogenetic position of the genus Hydrogenobacter.

The genus Hydrogenobacter consists of extremely thermophilic, obligately chemolithotrophic organisms that exhibit anaerobic anabolism but aerobic catabolism. Preliminary studies of the phylogenetic position of these organisms based on limited 16S ribosomal DNA sequence data suggested that they belong to one of the earliest branching orders of the Bacteria. In this study, the complete 16S ribosomal DNA sequences of two type strains, Hydrogenobacter thermophilus TK-6 and Calderobacterium hydrogenophilum Z-829, and another isolate, Hydrogenobacter sp. strain T3, were determined, and the phylogenetic positions of these organisms were examined. Our results revealed that the two type strains are members of a single genus, the genus Hydrogenobacter. Our results also verified the previous conclusion that the Aquifex-Hydrogenobacter complex belongs to a very early branching order, the "Aquificales." Within this order, the relationships among the various organisms are such that only a single family, the "Aquificaceae," can be recognized at this time. Given the early branching point of the "Aquificales," the characteristics of these organisms support the view that the last common ancestor of existing life was thermophilic and suggest that this ancestor may have fixed carbon chemoautotrophically.

Characteristics of CDC group 3 and group 5 coryneform bacteria isolated from clinical specimens and assignment to the genus Dermabacter.

Over a 1-year period, 11 isolates (including 5 from blood cultures) of the recently described CDC group 3 and group 5 coryneform bacteria were derived from clinical specimens and compared with reference strains. Biochemical characteristics indicated a very close relationship between CDC group 3 and group 5 coryneform bacteria. The ability of CDC group 3 and the inability of CDC group 5 coryneform bacteria to ferment xylose were the only reactions that were different for the two taxa. Chemotaxonomic features of the two groups included the presence of meso-diaminopimelic acid, a lack of mycolic acids, and the presence of predominantly branched cellular fatty acids, a combination found among gram-positive rods only in Brevibacterium spp., Brachybacterium faecium, and Dermabacter hominis. 16S rRNA gene sequence analysis revealed that CDC group 3 and group 5 coryneform bacteria are members of the genus Dermabacter, which to date has been isolated exclusively from human skin.

Characteristics of CDC group 1 and group 1-like coryneform bacteria isolated from clinical specimens.

Fifteen strains of CDC group 1 coryneform and biochemically similar bacteria were isolated from clinical specimens. Of the 15 strains isolated, 11 were derived from abscesses and purulent lesions, mostly from the upper part of the body, and 3 were grown from blood cultures. Nine strains were associated with mixed anaerobic but no other aerobic flora. Seven strains exhibited the classical biochemical profile of CDC coryneform group 1; however, eight strains were unable to reduce nitrate and were called "group 1-like." Other reactions to differentiate CDC group 1 and group 1-like coryneform rods include alpha-hemolysis on human blood agar, fermentation of adonitol, and the presence of alkaline phosphatase. Fifteen strains showed marked CAMP reactions on different erythrocyte agars. Gas-liquid chromatography of volatile and nonvolatile fatty acids as well as cellular fatty acid patterns and the composition of cell wall components suggest that CDC group 1 and group 1-like coryneform bacteria do not belong to the genus Corynebacterium but possibly to the genus Actinomyces or Arcanobacterium. DNA-DNA hybridization studies revealed that group 1 and group 1-like strains represent different species.